Modified polyvinyl acetal insulated conductors



May 27, 1958 J. A. LORITSCH EI'AL 2,336,513

MODIFIED POLYVINYL ACETAL INSULATED CONDUCTORS Filed Dec. 7. 1953 INSULATION caAn/ve COMPRISING PmrV/NYL ACETAL HES/N /COA/0'A/SA 7/0 P/woucr or A AZOEHVDE w/m 4 PRODUCT 0F HYD/PGLYS/S 0F 4 POL YI/l/VYL 5875/?) mm Inventors: John A. Loritsch, Edward W Daszewski,

b5 aka,

The] r Attorney.

United States Patent MODIFIED POLYVINYL ACETAL INSULATED CONDUCTDRS John A. Loritsch and Edward W. Daszewslri, Schenectady,

N. Y., assignors to General Electric i'lompany, a corporation oi New York Application December '7, 1953, Serial No. 396,582

6 Saints. (Cl. 117*232) This application is a continuation-in-part of our copending application Serial No. 376,620, filed August 26, 1953, now abandoned, and assigned to the assignee of the present invention.

This invention relates to resinous compositions and conductors insulated therewith. More particularly, the invention is concerned with improved enamels comprising polyvinyl acetals and to electrical conductors provided with such enamels.

Patnode and Flynn l atent 2,085,995, assigned to the assignee of the present invention, discloses insulated conductors provided with coating compositions comprising polyvinyl acetal resins. Although such insulated conductors have distinct advantages over conductors insulated with conventional oil-type enamels, the resinous compositions utilized therein are costly, and comparatively high priced solvents are required for the production of suitable Wire enamels therefrom. Jackson and Hall Patent 2,307,- 588, also assigned to the assignee of the present invention, discloses insulated conductors provided with an improved and less expensive resinous composition which additionally is soluble in relatively inexpensive solvents. Accordingly, insulated conductors having properties practically the same, and in certain respects even better than those described in the above Patnode et al. patent, can be made and at a substantially lower cost by combining suitable phenol-aldehyde resins with the polyvinyl acetal resin. Although conductors insulated with the Jackson and Hall compositions are eminently satisfactory for most applications, they do not possess the required solvent resistance necessary in certain instances, for example, when used in hermetically sealed motors of refrigerators. The attainment of adequate solvent resistance in addition to abrasion and heat resistance, as well as dielectric strength and other qualities possessed by the aforementioned Patnode and Flynn, and Jackson and Hall compositions has presented a problem, particularly to the magnet wire industry.

In accordance with the present invention, all of the useful advantages of the Patnode and Flynn, and Jackson and Hall compositions and insulated conductors are retained and markedly improved solvent resistance attained, by incorporating in polyvinyl acetal-phenol-aldehyde compositions, a condensate derived from the reaction of an aldehyde with an amino compound, namely, an ammonia derivative. The addition of a small amount, e. g., from 0.1% to by weight, imparts unexpectedly improved solvent resistance to the compositions and particularly to conductors or wires coated therewith.

The invention will be understood more readily from the following description when considered in connection with the accompanying drawing in which the single figure is a cross-sectional view of an electrical conductor provided with insulation in accordance with this invention.

The aldehyde-ammonia derivative condensates which are useful as additives herein are condensates formed by the known reaction of aldehydes, and particularly formaldehyde, with ammonia derivatives including amines and amides and, more particularly, with ureas and thioureas, etc., to form, e. g., urea-aldehyde condensates in the usual manner. Thus, aldehyde-amine and aldehyde-amide condensates are produced by the reaction of urea, thiourea and various substituted ureas and urea derivatives with aldehydes such as formaldehydes to form condensates, e. g., methylol ureas, etc. Various other amines and amides can similarly be reacted in known manner with formaldehyde, etc., to form condensates which are amine-aldehyde or amide-aldehyde resins or condensates.

The aldehyde-ammonia derivative condensates found eminently suitable for improving the solvent resistance of phenolic modified polyvinyl acetal compositions are the soluble condensates, i. e., the condensates which are soluble with and compatible with the resin composition. condensates having these properties and coming within the scope of the present invention are believed to have the grouping i ll.

wherein R is a radical of the class consisting of hydrogen, alkyl, aryl, alkaryl, aralkyl, a hetero oxygen-containing radical, forexample, furyl and R is a radical of the class consisting of hydrogen,

alkyl, aryl, alkaryl, aralkyl, a pyrrole residue, for example,

H o HC=0 l r (JJNH- and R in the second group having the same scope as in the first group, and n is an integer equal to or greater than one.

Included also are condensates of aldehydes and ammonia derivatives, particularly urea-aldehyde condensates, prepared in the presence of alcoholic or other solvents which take part in the reaction and thus 'become an integral part of the resulting resin composition, as Where butyl alcohol is present in the production of urea formaldehyde condensates to give butylated products.

The polyvinyl acetal resins employed in the process of this invention are hydrolyzed, polymerized vinyl ester aldehyde condensation products which may be produced from various aldehydes and various polyvinyl esters as more fully set forth in said Patnode et ,al. patent, and more fully described in Reissue Patent 20,430 to Morrison et al.

Aldehydes other than formaldehyde may be used in making polyvinyl acetal resins, for example, acetaldehyde, propionic aldehyde, butyric aldehyde, benzaldehyde and the like. Likewise, polyvinyl esters other than polyvinyl acetate may *be employed, for instance, polyvinyl propionate, polyvinyl butyrate and the like. The properties of polyvinyl acetal resins may 'be varied through a wide range by varying the viscosity and the extent of the hydrolysis of the polyvinyl ester, the amount and the character of the aldehyde reacted with the hydrolyzed poly- Patented May 27,1958

meriz ed vinyle'sfer, and the character and the amount of the acid catalyst used. 7

In order that those skilled in the art better may understandhow this invention may be carried into effect, the

following examples :are' given to" illustrateithef Prepare tion of phenolic-modified polyvinyl acetal enamels; W,here-; in an ammonia derivativeraldehyde condensate- 1si-em' resistance. As previously mentioned, one ofthe end uses of wires insulatingly coated with resinous compositions of the present type is in hermetically sealed motors used.

in refrigerators :where it is, subject 'to, the deleterious action of;'refrigerajnts 'such;as Freon. 'Test methods in-' volving the eifects of Freon per se on insulation are long and tedious irequiring special apparatus. Through a series'of tests, it .wasfound that there wasa correlation betweenfthe etfects ofj.,a-fifty-fiftymixture of solvents such as ethanoland toluene upon insulation of thepresent description and the action thereon of Freoh. This test was more severe than any other conditions which similarly insulated wires may encounter in use. Due to the ease of testing and the clos'eness in effect of 'such' a mixture to that of Freon, a fifty-fifty mixture of ethanol and toluen'e was used in all of the tests'which follow; i

test involved immersingthelengths of wires in a boiling mixture of 50 parts of alcohol,iforiexample,

. ethanol, and 50 parts of toluene for a total of lominutes,

This enamel was usedfto coat.0508" wire at various speeds ranging from; 14 feet per minute to 21 feetper after which time the wires were inspected for signs of of visible attack.

In the following examples, given by way of illustrationand not by way of'limit'ation, all parts and percentages are by weight.

Example] A resin having a solids content of 16% composed of 5 i e 7' K 7 5 Percent by weight Cresol-formaldehyde resin 5.33 Polyvinyl formal resin l. 10.67

Solvents, 84% formal compbsed of- Cresol 25.20 Naphtha 58.80

A phenol-aldehyde resin of the type disclosed in Jackson et al. Patent 2,307,588 which disclosure is incorporated herein by reference.

A part of this cresol the reaction vessel.

A V J 7 l1 Hie-onion n wherein n is greater than one. The butylated urea-formaldehyde condensate wasan 3 alcoholic -type"of ureaformaldehyde resinr'esulting from the reaction of the resin with an alcohol. (trade name Ufor'mite 240-N);

The resulting composition was agitated with a stirrer for approximately ene hour to insure good blending. It may be dyed, 1f des1red,.b'y adding a small amount of a suitabledye during the'stirring. Preferably, theenamel is filtered through ,a

pressure filter prior. to use foi 'namel ngwire.

minute to give an insulation thickness of 5 to 6 mils and was then tested for solvent resistance in accordance with the aforedescribed test. In each case, the solvent resistance was excellent.

Example 2 To the enamel of Example 1, 12%, by weight, based on the weight of resin solids represented by the poly-' vinyl formal resin, of trimethylol urea 'having the' formula was added in place of the butylated urea-formaldehyde condensate and the composition processed and tested for solvent resistance as in Example 1. Again in each case, the solvent resistance wasexcellent. e

Example To the enamel of Example 1 were addedin lieu of the butylated urea-formaldehyde condensate," various amounts of a pyrrole-formaldehyde condensate prepared by reacting formaldehyde with pyrrole in approximately equirnolecular proportion having the formula wherein n is greater than one, specifically from 0.3 to 12%, by weight, based on the weight of resin solids represented by the polyvinyl formal resin, and each composition processed and solvent tested as in Example 1.

The solvent resistance of each of the enamels tested was excellent. n

g 7 7 Example 4 'Various enamels were prepared,1containing from 0.3

. to 1.2%, by weight, based on the weight of resin solids The propenamou'nts of naphtha and cresol werehydecondensate.

represented by the polyvinyl formal resin, using the:

[ xamp 5 To the enamel of Example 1 was addedin placelof the butylated urea-formaldehyde condensate 0.3%, by weight, based on the weight of resin solids represented by the polyvinyl formal, of an aniline-formaldehyde con- 1 densate prepared by dissolving 100 parts of aniline in'SOO parts of 95% alcohol and refluxing with parts of 37% formaldehyde. 7 1

The resulting enamel was processedand its solvent re- 7 sistance tested as in Example 1 and again the solvent reistance was excellent. n,

. "E fl pleo Using the same composition and the same proportions of condensate as in Example 5, an aniline-acetaldehyde condensate prepared in similar manner was substituted and the resulting enamel solvent tested as in' previous.

examples; -This enamel also proved to have excellent solvent resistance; i

While the invention has been described with particular reference to cresol as'the phenolic ingredient in the modified polyvinyl acetal'resins, it will be obvious to;- those skilled in the art that otherphenolic bodies also In each case the, solvent remay be used, for example, those disclosed in Jackson et al. Patent 2,307,588, hereinabove incorporated by reference. Included are xylenols, mixtures of phenol and cresol or mixtures of phenol or cresol or phenol and cresol together with wood oil phenolic bodies of the kind described more fully in Patent No. 2,221,511 to Fiedler et al., dated November 12, 1940, and assigned to the same assignee as the present invention. Additional examples include the petrol-alkyl type phenols, which petroalkyl phenols may be used as the sole phenolic body or in combination with coal-tar phenol, cresols and other phenolic substances. Likewise, active methylene-containing bodies other than formaldehyde may be used, either in solid or solution state.

The properties of the phenol-aldehyde resin and accordingly the properties of the additive modified phenolaldehyde-polyvinyl acetal resinous compositions may be varied by varying the ratios of the phenolic body and the aldehyde. For example, resins containing 0.7 or more mols formaldehyde will convert to a substantially infusible insoluble state when heated at elevated temperatures whereas those containing 0.5 or 0.6 mol formaldehyde are thermoplastic. While for certain applications such thermoplastic resins may be used as modifying agents of the polyvinyl acetal resin in general, it is preferred to use in the preparation of wire enamels those phenolic resins which are produced by reacting 1 mol phenolic body with from 0.7 to 2.0 mols of an active methylene-containing body such as formaldehyde or other suitable aldehyde. No particular advantage is gained by using more than 2 mols formaldehyde to 1 mol of the phenolic body since the excess formaldehyde is volatilized during the cooking of the resin.

Enameled wires are produced by drawing the clean wire, for example, clean copper wire through a body of wire enamel made by incorporating the modifying phenolaldehyde resin, polyvinyl acetal resin, solvent and ammonia derivative-aldehyde condensate. The proportions of phenolic and polyvinyl acetal resins may be varied, for example, from, by weight, about 5 to 50 parts phenolic resins to form about 95 to 50 parts polyvinyl acetal resin. The total resin to solvent proportions also may be varied, for instance, from about 5 to 25 parts resin to about 95 to 75 parts solvent. It is preferred to use a phenolic resin-polyvinyl acetal resin ratio and a total resin-solvent ratio such as described under Example 1, since the particular combination of ingredients there described has been found to produce a wire enamel which is more readily and effectively applied to wire, and to yield an insulated wire having the most desirable combination of properties.

The concentrations of aldehyde-ammonia derivative condensate additive to phenolic resin modified polyvinyl acetal enamels found suitable to improve solvent resistance in accordance with the present invention is wide. Excellent results have been obtained by employing 0.1% to 5%, by weight, based on the weight of resin solids represented by the polyvinyl acetal resin. A preferred range is from 0.3 to 1.2%, by weight, based on the weight of resin solids represented by the polyvinyl acetal resin employed.

Various other solvents are equally as effective in the preparation of the herein-described enamels and are essentially the solvents disclosed in the aforesaid Jackson et al. patent.

The ammonia derivative-aldehyde condensates coming within the scope of the present invention are those which are substantially completely soluble in the enamel and compatible therewith. Condensates which are not soluble or only slightly soluble or which are incompatible with the enamel are ineffective for the present purposes. Al-

though the invention has been described more fully in I is substantially completely soluble and compatible with the enamel and which generally has the previously defined grouping Li ll.

may be employed. Illustrative examples of aldehydes condensible with an gmmonia derivative to give the present condensates include, in addition to the formaldehyde and acetaldehyde of the examples, for instance, propionaldehyde, n-butyraldehyde, isobutyraldehyde, nvaleraldehyde, isovaleraldehyde, n-caproaldehyde, etc., benzaldehyde and the like.

The method of coating the aforedescribed wires was in accordance with the procedure disclosed in the Jackson et al. patent. For example, after the wire had been passed through a bath containing the particular wire enamel, the coated wire was subjected to heat by introducing it into a suitable oven wherein the enamel was baked at a suitable temperature, for example, at an oven temperature of about 250 to 500 C. The coating was baked simultaneously with the annealing of the copper. As previously mentioned, the wire was drawn through the bath at various speeds ranging from 14 feet per minute to 21 feet per minute. Usually, it was necessary to run the wire successively through the enamel bath and baking oven several times at a constant speed in order to provide adequate insulation thereon. Baking at the previously mentioned temperatures advanced the phenol-aldehyde component of the mixed or combined resin film to the insoluble infusible state, and likewise improved the properties of the polyvinyl acetal resin component. The hardness, abrasion resistance, and resistance of the resin film to attack by oils, solvents, varnishes and various chemicals were improved by such treatment. Wires coated with the instantly described enamels gave results comparable with those resulting from the tests described and illustrated in Patent No. 2,307,588 on the phenol-aldehyde modified polyvinyl acetal enamels therein described. However, there was a substantial improvement in the solvent resistance of the present enamels. Whereas the prior enamel failed completely under the solvent resistant tests hereinbefore described, each of the present enamels containing a condensate of an ammonia derivative and an aldehyde showed excellent solvent resistance under the same conditions. Additionally, it should be noted that the solvent resistant test employed in the instant process is a far more vigorous test than that of the aforementioned patent.

It is to be understood that this invention is not limited to the application of the new insulating composition directly upon the conductor as illustrated in the accompanying drawing but may also be applied in accordance with the methods described and illustrated in the Jackson et al. patent.

Although the phenolic resin modified polyvinyl acetal resin having incorporated therein an ammonia derivativealdehyde condensate is particularly applicable to the manufacture of wire enamels and insulated conductors, it will be appreciated that its field of utility is not limited thereto. For'example, it may be used to improve the solvent resistance of phenolic resin-modified polyvinyl acetal resin heretofore used as an adhesive for cementing together such materials as mica flakes to form bonded mica sheet insulation, as a cementing agent to bond together fibrous materials in sheet, tape, felted, or other form and as a coil impregnating varnish.

The additive containing phenolic resin modified polyvinyl acetal resins may be made in the form of solvent resistant thin sheets or tapes and used alone or adhesively bonded to, or otherwise in combination with, other materials such as paper, cellulose, esters, cellulose ethers, etc., as coil layer insulation. Such sheets or tapes having improved solvent resistance also may be applied to a conductor, according to well-knownstrip covering meth-r od s, as insulationtherefon} They may be heat-treated to improve their properties either before, during application.

What We claim as new and desire to secure by Letters Patent of the United Statesis:-

I. An insulated copper conductor in which the outer insulation therefor comprises essentially a hard, flexible, tough, abrasion-resistant and Freon-resistant coating, said coating being the' heat-treated product of a mixture of ingredients consisting essentially, by weight, of (1) from 95 to 50 percent of a polyvinyl formal resin obtained 7 by condensing formaldehyde with a product of hydrolysis of polyvinyl acetate, (2) from to 50 percentrof a heat -hardenable resin obtained by condensing a phenol selected from the class consisting of phenol, cresol,

2,ss.e,51er

o fte v xylenol andmixtures thereof, with formaldehyde in the a ratio of one mol'oftthe' phenol to 0.7 to 2 mols of the formaldehyde inithe presence of an alkaline catalyst, (3)-' from 0.3 to 1.2 percent, based on the weight of resin jsolids represented by the polyvinyl formal resin;

of a condensation product selected fromtthe group consisting of urea-aldehyde, alkylated urea aldehyde, pyrrolealdehyde, aromatic amine aldehyde, and thiourea-aldehyde condensates, and (4) a solvent in which (1), (2) and ,(3); are soluble composed of a mixture of cresol and naphtha, the solids content of the treating solution for'the conductor being composed, by Weight, of from 5 to 25 parts of rthe above-described resinous ingredients 'to about 75 to ,95 parts of the cresol naphtha solvent.

,2. insulated electrical conductor of claim 1, in

which the condensation product contained in the insulation comprises a butylated urea-formaldehydecondensate,v 3.' T he insulated electrical conductor of claim 1 in;

which the condensation product contained 7 in t i ular tion comprises trimethylol, ureali 4. The insulated electrical conductor of claim whichthe condensation product in the insulation comprises a pyrrole-formaldehyde condensate.

5; The insulated electrical conductor of claim 1 in which the condensation product containedin the insula-- tion comprises an aniline-formaldehydecondensate.

6. The insulated electrical conductor of claim'l in which the condensation product contained in the'insulation comprises an aniline-acetaldehyde condensate.

References Cited in the file of this patent UNITED STATES PATENTS Australia Nov. 14, 19 51- 

1. AN INSULATED COOPER CONDUCTOR IN WHICH THE OTHER INSULATION THEREFOR COMPRISES ESSENTIALLY A HARD, FLEXIBLE TOUGH, ABRASION-RESISTANT AND FREON-RESISTANT COATING, SAID COATING BEING THE HEATED-TREATED PRODUCT OF A MIXTURE OF INGREDIENTS CONSISTING ESSENTIALLY, BY WEIGHT, OF (1) FROM 95 TO 50 PERCENT OF A POLYVINYL FORMAL RESIN OBTAINED BY CONDENSING FORMALDEHYDE WITH A PRODUCT OF HYDROLYSIS OF POLYVINYL ACETATE, (2) FROM 5 TO 50 PERCENT OF A HEAT-HARDENABLE RESIN OBTAINED BY CONDENSING A PHENOL SELECTED FROM THE CLASS CONSISTING OF PHENOL, CRESOL, XYLENOL AND MIXTURES THEREOF, WITH FROMALDEHYDE IN THE RATIO OF ONE MOL OF THE PHENOL TO 0.7 TO 2 MOLS OF THE FORMALDEHYDE IN THE PRESENCE OF AN ALKALINE CATAYLST, (3) FROM 0.3 TO 1.2 PERCENT, BASED ON THE WEIGHT OF RESIN SOLIDS REPRESENTED BY THE POLYVINYL FORMAL RESIN, OF A CONDENSATION PRODUCT SELECTED FROM THE GROUP CONSISTING OF UREA-ALDEHYDE, ALKAYLATED UREA ALDEHYDE, PYRROLEALDEHYLE, AROMATIC AMINE ALJEDYDE, AND THIOUREA-ALDEHYDE CONDENSATES, AND (4) A SOLVENT IN WHICH (1), (2) AND (3) ARE SOLUBLE COMPOSED, BY WEIGHT, OF FROM AND NAPTHA, THE SOLIDS CONTENT OF THE TREATING SOLUTION FOR THE CONDUCTOR BEING COMPOSED, BY WEIGHT, OF FROM 5 TO 25 PARTS OF THE ABOVE-DESCRIBED RESINOUS INGREDIENTS TO ABOUT 75 TO 95 PARTS OF THE CRESOL NAPTHA SOLVENT. 